1. Field of the Invention
The invention relates to the field of quantum physics of condensed media and, more particularly, to methods for forming quantum collective excitations of spin density and magnetization density in graphene films, and may be used in quantum nanoelectronics, spintronics, for creating spin-processors, memory cells, physical field sensors, other devices and systems for processing and storing information of terahertz (and higher) range that have nanometric dimensions and work in a broad temperature range with minimum energy consumption.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Graphene, which is a monoatomic two-dimensional hexagonal lattice of carbon atoms, is considered as one of basic materials for creating a circuitry of nanoelectronic spintronic devices and systems that ensure a several-digits gain in the fields of speed, dimensions and energy consumption as compared to microelectronic analogous solutions. This is conditioned by the fact that a ferromagnetic effect has been observed experimentally and discussed theoretically in such a structure in a broad temperature range (from several degrees to 500 K), which effect proves that graphene structures may have intrinsic magnetization conditioned by non-zero spin density of atom valence electrons that is distributed over two-dimensional carbon lattice [Wang, Y., Huang, Y., Song, Y., Zhang, X., Ma, Y., Liang, J., and Chen, Y. Room-Temperature Ferromagnetism of Graphene. Nano Leu. 9, 220-224 (2009)], [D. V. Kolesnikov and V. A. Osipov The continuum gauge field-theory model for low-energy electronic states of icosahedral fullerenes, Joint Institute for Nuclear Research, Bogoliubov Laboratory of Theoretical Physics, arXiv:cond-mat/0510636,v2,2,Feb,2006.14], [Gusynin V. P. et al. “Unconventional Integer Quantum Hall Effect in Graphene”. Phys., Rev. Lett. 95, 146801, (2005), DOI:10.1103/PhysRevLett.95.146801], [Peres N.M.R., et. al. Electronic properties of disordered two-dimensional carbon Phys. Rev. B 73, 125411 (2006) DOI:10.1103/PhysRevB.73.125411], [Novoselov K. S. et al. “Two-dimensional gas of massless Dirac fermions in graphene”, Nature 438, 197 (2005) DOI:10.1038/nature04233], [Zhang Y. et. al. “Experimental observation of the quantum Hall effect and Berry's phase in graphene” Nature 438, 201 (2005) DOI:10.1038/nature04235], [K. Ziegler Derealization of 2D Dirac Fermions: The Role of a Broken Supersymmetry. Phys. Rev. Lett. 80, 3113-3116 (1998)], [J. Alicea. Matthew P. A. Fisher. Graphene integer quantum Hall effect in the ferromagnetic and paramagnetic regimes, Phys. Rev. B 74, 075422 (2006)], [N.M.R. Peres, F. Guinea, A. H. Castro Neto. Coulomb interactions and ferromagnetism in pure and doped graphene. PHYSICAL REVIEW B 72, 174406 (2005)], [N. Tombros, C. Jozsa, M. Popinciuc, H. T. Jonkman, B. J. van Wees. Electronic spin transport and spin precession in single graphene layers at room temperature. arXiv:0706.1948, Nature 448, 571-574 (2007)], [Nguyen Viet Hung, A. Bournel, P. Dollfus, Nguyen Van Lien. Spin-dependent transport in double ferromagnetic-gate graphene structures, Journal of Physics: Conference Series 187 (2009), 012037,doi:10.1088/1742-6596/187/1/012037], [D. D. Grachev, Yu. P. Rybakov, L. A. Sevastianov, Ye. F. Sheka “Ferromagnetism in graphene and fullerene nanostructures. Theory, simulation, experiment.” M. UDN Newsletter, 2010], [G. M. Arzumanyan, E. A. Ayrjan, D. D. Grachev, L. A. Sevastianov. Quantum Field Model for Graphene Magnetism], [D. D. Grachev, L. A. Sevastianov. Quantum Field Approach to the Ferromagnetic Properties of the Graphene Films. Int. Conference of Theoretical Physics “Dubna-Nano2010”, p. 63. Dubna, JINR, 2010].
The availability of this non-zero spin density enables to control its distribution with the use of various physical fields, and this forms a basis for creating spintronic elements and devices. For creating such devices it is necessary to form local excitations of spin density, which are subjected to a control action.
A method is known that is used for forming spin waves by tunneling spin-polarized electrons to a graphene film from a cobalt electrode through a dielectric insulating film [N. Tombros, C. Jozsa, M. Popinciuc, H. T. Jonkman, B. J. van Wees. Electronic spin transport and spin precession in single graphene layers at room temperature. arXiv:0706.1948, Nature 448, 571-574 (2007)].
Injected electrons form spin spatially localized pulses that later propagate and relax in a graphene film. During measurements local magnetic resistance and precession of injected spins in an external magnetic field are registered. A relaxation time is about 100 picoseconds, and a relaxation length is about 1-2 microns.
A limitation of this known method is the absence of quantum coherence of spin pulses formed, this restricts their lifetime and length of relaxation on a graphene surface, which are important for various practical applications.